Nepal travel insurance

Hi,

I'm travelling to Nepal for a few days to do some trekking of up to 3000 metres and already have an annual worldwide cover travel policy which includes trekking to this altitude, however it doesn't cover search and rescue, i.e. helicopter rescue in the event of an accident.

I'd like to get cover for this portion and found WorldNomads and others who offer this as part of their policy but they are in excess of £120 for 6 days cover, partly based on some insurance fraud with search and rescue services in Nepal.

I'm actually only trekking for 4 days and arriving from a week in India but originating from the UK and coming back to the UK from Nepal via India again.

I've a few questions on this:

1. Can I just take out 4 days insurance for the trekking period rather than the 6 days since I already have insurance to cover me for my travel to and from Nepal?
2. Would there be any implications on the 4 days cover not originating in the UK, since I will be coming from India?

Any help would be much appreciated.

TIA